(1) Field of the Invention
The invention relates to a technology for locking on a specific satellite, and more particularly to the technology that utilizes scanned data to lock on the target satellites.
(2) Description of the Prior Art
Satellite technology has been improving human life in its various aspects. In daily life, positioning apparatuses, mobile phones, broadcasting apparatuses, navigation devices, and other devices using global positioning system (GPS) had drawn people closer geographically and had visualized the image of global community. In particular, the achievement in broadcasting via satellites has realized the “real-time” TV programs in broadcasting industry, and has made it possible to play varieties of programs at any corner around the world.
In the prior art, the satellite broadcasting technology can he roughly classified into a type of stationary broadcasting or a type of mobile broadcasting. The type of stationary broadcasting is to have a satellite antenna system mounted on the ground or at a suitable fixed construction. In such type of broadcasting, satellite parameters are initially downloaded, then the antenna system is actuated to aim at the target satellite, and to establish a bi-directional signal and data link between the station and the satellite. The type of stationary broadcasting can only provide a limited space coverage, due to its immobility, and it is quite possibly that the signal broadcasted as DVB-T (Digital Video Broadcasting-Terrestrial) cannot be reached.
For the aforesaid disadvantage of limited space coverage in the stationary broadcasting, the mobile broadcasting, provides an alternative solution thereto, One of the main applications in the mobile broadcasting is the satellite news gathering (SNG) vehicle, The SNG vehicle provides an on-top antenna system for tracking satellites and for processing bi-directional signal and data communication as soon as the target satellite is locked on.
In the case that the tracking target of the antenna system for mobile broadcasting is shifted from one satellite to another, the satellite parameters of another satellite are needed to be pre-stored in the database of the antenna system in order to establish an effective communication between the satellites and the ground, In practice, the database of the antenna system can pre-store parameters of all prospective satellites in the space, and actually a change in the satellite tracking is as simple as a task of control choice in operating the antenna system. According to the satellite parameters (especially the coordinate parameters), the antenna dish of the antenna system can be precisely pivoted to direct the target satellite, Alternatively, the antenna system can also obtain the satellite parameters from an earth satellite transmission station or a satellite control center, while a new tracking starts.
In practice, the ability of an antenna system to successfully lock on an orbiting satellite, it mainly depends on the following three coordinate factors: celestial coordinates of the satellite including a right ascension (R.A.) angle (RA angle, hereinafter) and a declination (Decl.) angle (Decl angle, hereinafter), geographic coordinates of the antenna system (i.e. the SNG vehicle) including longitude and a latitude, and the pointing angles of attitude related to the vehicle including an azimuth angle and an elevation angle.
In the prior art, the final orientation of the antenna pointing to the specified satellite is primarily decided by combining those satellite coordinates and those corrected parameters related to an azimuth angle and an elevation angle which had been initially integrated into a satellite antenna system. However, the vehicle of the antenna system moves arbitrarily and is subjected to possible mechanical vibrations, certain deviations might be expected during the process of satellite tracking carried out by the antenna configured onboard of the vehicle by adopting those corrected parameters which had been accepted as reference values initially. Consequently, after a substantial period of operation by using the satellite data input and coordinate captured, it is questionable to maintain the mobile satellite dish to precisely lock on the target satellite.
Therefore, an improved satellite lock-on technique for a mobile antenna system to precisely and promptly lock on an orbiting satellite definitely provides a technical solution to the ordinary person skilled in the art.